Formulation for spray-drying large porous particles

ABSTRACT

Particles having a tap density less than about 0.4 g/cm3 are formed by spray drying from a colloidal solution including a carboxylic acid or salt thereof, a phospholipid, a divalent salt and a solvent such as an aqueous-organic solvent. The colloidal solution can also include a therapeutic, prophylactic or diagnostic agent. Preferred carboxylic acids include at least two carboxyl groups. Preferred phospholipids include phosphatidylcholines, phosphatidylethanolamines, phosphatidylglycerols, phophstidylserines, phosphatidylinositols and combinations thereof. The particles are suitable for pulmonary delivery.

RELATED APPLICATION

[0001] This application is a divisional of U.S. Ser. No.: 09/644,105,filed Aug. 23, 2000, which claims the benefit of U.S. ProvisionalApplication No. 60/461,874 filed on Apr. 10, 2003. The entire teachingsof the above application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] Aerosols for the delivery of therapeutic agents to therespiratory tract have been described, for example, Adjei, A. andGarren, J.,Pharm. Res., 7: 565-569 (1990); and Zanen, P. and Lamm, J.-W.J. Int. J Pharm., 114: 111-115 (1995). The respiratory tract encompassesthe upper airways, including the oropharynx and larynx, followed by thelower airways, which include the trachea followed by bifurcations intothe bronchi and bronchioli. The upper and lower airways are called theconducting airways. The terminal bronchioli then divide into respiratorybronchioli which then lead to the ultimate respiratory zone, thealveoli, or deep lung. Gonda, I. “Aerosols for delivery of therapeuticand diagnostic agents to the respiratory tract,” in Critical Reviews inTherapeutic Drug Carrier Systems, 6: 273-313 (1990). The deep lung, oralveoli, are the primary target of inhaled therapeutic aerosols forsystemic drug delivery.

[0003] Inhaled aerosols have been used for the treatment of local lungdisorders including asthma and cystic fibrosis (Anderson, Am. Rev.Respir. Dis., 140: 1317-1324 (1989)) and have potential for the systemicdelivery of peptides and proteins as well (Patton and Platz, AdvancedDrug Delivery Reviews, 8: 179-196 (1992)). However, pulmonary drugdelivery strategies present many difficulties for the delivery ofmacromolecules; these include protein denaturation duringaerosolization, excessive loss of inhaled drug in the oropharyngealcavity (often exceeding 80%), poor control over the site of deposition,lack of reproducibility of therapeutic results owing to variations inbreathing patterns, the frequent too-rapid absorption of drugpotentially resulting in local toxic effects, and phagocytosis by lungmacrophages.

[0004] Considerable attention has been devoted to the design oftherapeutic aerosol inhalers to improve the efficiency of inhalationtherapies. Timsina et. al., Int. J Pharm., 101: 1-13 (1995); and Tansey,I. P., Spray Technol. Market, 4: 26-29 (1994). Attention has also beengiven to the design of dry powder aerosol surface texture, regardingparticularly the need to avoid particle aggregation, a phenomenon whichconsiderably diminishes the efficiency of inhalation therapies. French,D. L., Edwards, D. A. and Niven, R. W., J. Aerosol Sci., 27: 769-783(1996). Dry powder formulations (“DPFs”) with large particle size haveimproved flowability characteristics, such as less aggregation (Visser,J., Powder Technology 58: 1-10 (1989)), easier aerosolization, andpotentially less phagocytosis. Rudt, S. and R. H. Muller, J. ControlledRelease, 22: 263-272 (1992); Tabata, Y. and Y. Ikada, J. Biomed. Mater.Res., 22: 837-858 (1988). Dry powder aerosols for inhalation therapy aregenerally produced with mean geometric diameters primarily in the rangeof less than 5 μm. Ganderton, D., J. Biopharmaceutical Sciences, 3:101-105 (1992); and Gonda, I. “Physico-Chemical Principles in AerosolDelivery,” in Topics in Pharmaceutical Sciences 1991, Crommelin, D. J.and Midha, K. K., Eds., Medpharm Scientific Publishers, Stuttgart, pp.95-115, 1992. Large “carrier” particles (containing no drug) have beenco-delivered with therapeutic aerosols to aid in achieving efficientaerosolization among other possible benefits. French, D. L., Edwards, D.A. and Niven, R. W., J. Aerosol Sci., 27: 769-783 (1996).

[0005] The human lungs can remove or rapidly degrade hydrolyticallycleavable deposited aerosols over periods ranging from minutes to hours.In the upper airways, ciliated epithelia contribute to the “mucociliaryescalator” by which particles are swept from the airways toward themouth. Pavia, D. “Lung Mucociliary Clearance,” in Aerosols and the Lung:Clinical and Experimental Aspects, Clarke, S. W. and Pavia, D., Eds.,Butterworths, London, 1984. Anderson, Am. Rev. Respir. Dis., 140:1317-1324 (1989). In the deep lungs, alveolar macrophages are capable ofphagocytosing particles soon after their deposition. Warheit, M. B. andHartsky, M. A., Microscopy Res. Tech., 26: 412-422 (1993); Brain, J. D.,“Physiology and Pathophysiology of Pulmonary Macrophages,” in TheReticuloendothelial System, Reichard, S. M. and Filkins, J., Eds.,Plenum, New York, pp. 315-327, 1985; Dorries, A. M. and Valberg, P. A.,Am. Rev. Resp. Disease 146: 831-837 (1991); and Gehr, P., MicroscopyRes. and Tech., 26: 423-436 (1993). As the diameter of particles exceeds3 μm, there is increasingly less phagocytosis by macrophages. Kawaguchi,H., Biomaterials 7: 61-66 (1986); Krenis, L. J. and Strauss, B., Proc.Soc. Exp. Med., 107: 748-750 (1961); and Rudt, S. and Muller, R. H., J.Contr. Rel., 22: 263-272 (1992). However, increasing the particle sizealso has been found to minimize the probability of particles (possessingstandard mass density) entering the airways and acini due to excessivedeposition in the oropharyngeal or nasal regions. Heyder, J., J. AerosolSci., 17: 811-825 (1986).

[0006] Local and systemic inhalation therapies can often benefit from arelatively slow controlled release of the therapeutic agent. Gonda, I.,“Physico-chemical principles in aerosol delivery,” in: Topics inPharmaceutical Sciences 1991, D. J. A. Crommelin and K. K. Midha, Eds.,Stuttgart: Medpharm Scientific Publishers, pp. 95-117 (1992). Slowrelease from a therapeutic aerosol can prolong the residence of anadministered drug in the airways or acini, and diminish the rate of drugappearance in the bloodstream. Also, patient compliance is increased byreducing the frequency of dosing. Langer, R., Science, 249: 1527-1533(1990); and Gonda, I., “Aerosols for delivery of therapeutic anddiagnostic agents to the respiratory tract,” in Critical Reviews inTherapeutic Drug Carrier Systems 6: 273-313 (1990).

[0007] Controlled release drug delivery to the lung may simplify the wayin which many drugs are taken. Gonda, I., Adv. Drug Del. Rev., 5: 1-9(1990); and Zeng, X., et al., Int. J. Pharm., 124: 149-164 (1995).Pulmonary drug delivery is an attractive alternative to oral,transdermal, and parenteral administration because self-administrationis simple, the lungs provide a large mucosal surface for drugabsorption, there is no first-pass liver effect of absorbed drugs, andthere is reduced enzymatic activity and pH mediated drug degradationcompared with the oral route. Relatively high bioavailability of manymolecules, including macromolecules, can be achieved via inhalation.Wall, D. A., Drug Delivery, 2: 1-20 1995); Patton, J. and Platz, R.,Adv. Drug Del. Rev., 8: 179-196 (1992); and Byron, P., Adv. Drug. Del.Rev., 5: 107-132 (1990). As a result, several aerosol formulations oftherapeutic drugs are in use or are being tested for delivery to thelung. Patton, J. S., et al., J. Controlled Release, 28: 79-85 (1994);Damms, B. and Bains, W., Nature Biotechnology (1996); Niven, R. W., etal., Pharm. Res., 12(9): 1343-1349 (1995); and Kobayashi, S., et al.,Pharm. Res., 13(1): 80-83 (1996).

[0008] Drugs currently administered by inhalation come primarily asliquid aerosol formulations. However, many drugs and excipients,especially proteins, peptides (Liu, R., et al., Biotechnol. Bioeng., 37:177-184 (1991)), and biodegradable carriers such aspoly(lactide-co-glycolides) (PLGA), are unstable in aqueous environmentsfor extended periods of time. This can make storage as a liquidformulation problematic. In addition, protein denaturation can occurduring aerosolization with liquid formulations. Mumenthaler, M., et al.,Pharm. Res., 11: 12-20 (1994). Considering these and other limitations,dry powder formulations (DPF's) are gaining increased interest asaerosol formulations for pulmonary delivery. Damms, B. and Bains, W.,Nature Biotechnology (1996); Kobayashi, S., et al., Pharm. Res., 13(1):80-83 (1996); and Timsina, M., et al., Int. J. Pharm., 101: 1-13 (1994).However, among the disadvantages of DPF's is that powders of ultrafineparticulates usually have poor flowability and aerosolizationproperties, leading to relatively low respirable fractions of aerosol,which are the fractions of inhaled aerosol that escape deposition in themouth and throat. Gonda, I., in Topics in Pharmaceutical Sciences 1991,D. Crommelin and K. Midha, Editors, Stuttgart: Medpharm ScientificPublishers, 95-117 (1992). A primary concern with many aerosols isparticulate aggregation caused by particle-particle interactions, suchas hydrophobic, electrostatic, and capillary interactions. An effectivedry-powder inhalation therapy for both short and long term release oftherapeutics, either for local or systemic delivery, requires a powderthat displays minimum aggregation, as well as a means of avoiding orsuspending the lung's natural clearance mechanisms until drugs have beeneffectively delivered.

[0009] Therefore, a need exists for dry-powders suitable for inhalationwhich minimize or eliminate the above-mentioned problems.

SUMMARY OF THE INVENTION

[0010] The invention relates to particles having a tap density of lessthan about 0.4 g/cm³ and preferably less than about 0.1 g/cm³. Theparticles include a carboxylate group or moiety. The particles furtherinclude a multivalent salt or its ionic components. In one embodiment ofthe invention, the particles further include a phospholipid. Inaddition, the particles can include a therapeutic, prophylactic ordiagnostic agent or any combination thereof. In one embodiment, theparticles have a median geometric diameter of between about 5 microns(μm) and about 30 μm, preferably at least about 9 μm. In anotherembodiment, the particles have an aerodynamic diameter of between about1 μm and about 5 μm.

[0011] The invention also relates to a method of producing particleshaving a tap density of less than about 0.4 g/cm³. The method includesforming a mixture which includes a carboxylate moiety, such as provided,for example, by a carboxylic acid or salt thereof, a multivalent salt, aphospholipid, and a solvent. The mixture can also include a therapeutic,prophylactic or diagnostic agent, or any combination thereof. Themixture is spray-dried to form particles having a tap density of lessthan about 0.4 g/cm³. Preferred solvents that can be employed in thespray drying process include organic or organic-aqueous solvents. In apreferred embodiment, the mixture fed to the spray drying apparatus is acolloidal suspension.

[0012] The invention further relates to a method of delivering atherapeutic, prophylactic or diagnostic agent to the pulmonary system ofa patient in need of treatment, prophylaxis or diagnosis. The methodincludes administering to the respiratory tract of the patient aneffective amount of particles having a tap density of less than about0.4 g/cm³ and preferably less than about 0.1 g/cm³. The particlesinclude a therapeutic, prophylactic or diagnostic agent, or anycombination thereof and a carboxylate moiety. The particles furtherinclude a multivalent salt or its ionic components. In one embodiment ofthe invention, the particles also include a phospholipid. Delivery tothe respiratory system can be primarily to the deep lung, to the centralairways or to the upper airways.

[0013] The invention relates also to a composition for delivery to apatient in need of treatment, prophylaxis or diagnosis. The compositionincludes particles which have a tap density of less than about 0.4 g/cm³and preferably less than about 0.1 g/cm³. In one embodiment, theparticles include a carboxylate moiety, a multivalent salt and aphospholipid. In a preferred embodiment, the particles also include atherapeutic, prophylactic or diagnostic agent. In another preferredembodiment, delivery is to the pulmonary system.

[0014] In a preferred embodiment, the carboxylate moiety is ahydrophilic carboxylic acid or salt thereof. In another embodiment,preferred carboxylate moieties include at least two carboxyl groups.

[0015] In a preferred embodiment, the salt is a divalent salt. Suitabledivalent salts include, for example chlorides of alkaline earth metals.Calcium chloride (CaCl₂) is preferred. In another preferred embodiment,the multivalent salt is a pharmaceutically acceptable salt.

[0016] Preferred phospholipids include but are not limited tophosphatidic acid, phosphatidylcholines, phosphatidylethanolamines,phosphatidylglycerols, phosphatidylserines, phosphatidylinositols andcombinations thereof.

[0017] The invention has several advantages. Pulmonary deliveryadvantageously can reduce or eliminate the need for injection. Forexample, the requirement for daily insulin injections can be avoided.Furthermore, the particles of the invention can be delivered as a drypowder to the deep lung, upper or central airways. They can be used toprovide controlled systemic or local delivery of therapeutic ordiagnostic agents to the respiratory tract via aerosolization. Theparticles can be easily prepared from simple, lung-compatible compoundswithout requiring the use of large macromolecules such as polymers,proteins, polysaccharides and others. The formation of colloidalsuspensions results in particles of desired shape and porosity. Comparedto methods that require solubilizing, higher concentrations can beemployed. Administration of the particles to the lung by aerosolizationpermits deep lung delivery of relatively large diameter therapeuticaerosols, for example, greater than about 5 μm in mean diameter. Theparticles can be fabricated with a rough surface texture to reduceparticle agglomeration and improve flowability of the powder. Thespray-dried particle can be fabricated with features which enhanceaerosolization via dry powder inhaler devices, and lead to lowerdeposition in the mouth, throat and inhaler device.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The features and other details of the invention, either as stepsof the invention or as combination of parts of the invention, will nowbe more particularly described and pointed out in the claims. It will beunderstood that the particular embodiments of the invention are shown byway of illustration and not as limitations of the invention. Theprinciple feature of this invention may be employed in variousembodiments without departing from the scope of the invention.

[0019] The invention is directed to particles having a tap density ofless than about 0.4 g/cm³ and preferably less than about 0.1 g/cm³ andto methods of producing such particles. The particles can be employedfor delivery of a therapeutic, prophylactic or diagnostic agent to apatient in need of therapy, prophylaxis or diagnosis. In a preferredembodiment, delivery is to the pulmonary system. The particles can alsobe delivered to nonhuman mammals such as, for example, to laboratoryanimals or in veterinary medicine.

[0020] The particles include a carboxylate moiety. In one embodiment ofthe invention, the carboxylate moiety includes at least two carboxylgroups. Carboxylate moieties can be provided by carboxylic acids, saltsthereof as well as by combinations of two or more carboxylic acidsand/or salts thereof. In a preferred embodiment, the carboxylate moietyis a hydrophilic carboxylic acid or salt thereof. Suitable carboxylicacids include but are not limited to hydroxydicarboxylic acids,hydroxytricarboxilic acids and the like. Citric acid and citrates, suchas, for example sodium citrate, are preferred. Combinations or mixturesof carboxylic acids and/or their salts also can be employed.

[0021] The carboxylate moiety can be present in the particles in anamount ranging from about 10 to about 80% weight. Preferably, thecarboxylate moiety can be present in the particles in an amount 10-20%.

[0022] The particles also include a multivalent salt or its ioniccomponents. As used herein, a “multivalent” salt includes divalentsalts. In a preferred embodiment, the salt is a divalent salt. Inanother preferred embodiment, the salt is a salt of an alkaline-earthmetal, such as, for example, calcium chloride. The particles of theinvention can also include mixtures or combinations of salts and/ortheir ionic components.

[0023] The salt or its ionic components are present in the particles inan amount ranging from about 5 to about 40% weight.

[0024] The particles further include a phospholipid, also referred toherein as phosphoglyceride. In a preferred embodiment, the phospholipid,is endogenous to the lung. In another preferred embodiment thephospholipid includes, among others, phosphatidic acid,phosphatidylcholines, phosphatidylethanolamines, phosphatidylglycerols,phophatidylserines, phosphatidylinositols and combinations thereof.Specific examples of phospholipids include but are not limited tophosphatidylcholines dipalmitoyl phosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamine (DPPE), distearoyl phosphatidylcholine (DSPC),dipalmitoyl phosphatidyl glycerol (DPPG) or any combination thereof.

[0025] The phospholipid can be present in the particles in an amountranging from about 20 to about 90% weight. Preferably, it can be presentin the particles in an amount ranging from about 50 to about 80% weight.

[0026] Suitable methods of preparing and administering particles whichinclude phospholipids, are described in U.S. Pat. No. 5,855,913, issuedon Jan. 5, 1999 to Hanes et al. and in U.S. Pat. No. 5,985,309, issuedon Nov. 16, 1999 to Edwards et al. The teachings of both areincorporated herein by reference in their entirety.

[0027] In another embodiment of the invention the particles include asurfactant such as, but not limited to the phospholipids describedabove. Other surfactants, such as, for example, hexadecanol; fattyalcohols such as polyethylene glycol (PEG); polyoxyethylene-9-laurylether; a surface active fatty acid, such as palmitic acid or oleic acid;glycocholate; surfactin; a poloxomer; a sorbitan fatty acid ester suchas sorbitan trioleate (Span 85); tyloxapol can also be employed.

[0028] As used herein, the term “surfactant” refers to any agent whichpreferentially absorbs to an interface between two immiscible phases,such as the interface between water and an organic polymer solution, awater/air interface or organic solvent/air interface. Surfactantsgenerally possess a hydrophilic moiety and a lipophilic moiety, suchthat, upon absorbing to microparticles, they tend to present moieties tothe external environment that do not attract similarly-coated particles,thus reducing particle agglomeration. Surfactants may also promoteabsorption of a therapeutic or diagnostic agent and increasebioavailability of the agent.

[0029] The surfactant can be present in the particles in an amountranging from about 20 to about 90. Preferably, it can be present in theparticles in an amount ranging from about 50 to about 80.

[0030] Examples of therapeutic, prophylactic or diagnostic agents, alsoreferred to herein as “bioactive agents”, “drugs” or “medicaments”, bothlocally as well as systemically acting agents. The particles can alsoinclude mixtures of therapeutic, prophylactic and/or diagnostic agents.Furthermore, the particles can include needed biological compounds suchas, for example, blood, plasma or oxygen. The particles can includehydrophilic as well as hydrophobic drugs.

[0031] Examples of therapeutic, prophylactic or diagnostic agentsinclude, but are not limited to synthetic inorganic and organiccompounds, proteins, peptides, polypeptides, polysaccharides and othersugars, lipids, and DNA and RNA nucleic acid sequences havingtherapeutic, prophylactic or diagnostic activities. Nucleic acidsequences include genes, antisense molecules which bind to complementaryDNA or RNA and inhibit transcription, and ribozymes. Polysaccharides,such as heparin, can also be administered. The agents to be incorporatedcan have a variety of biological activities, such as vasoactive agents,neuroactive agents, hormones, anticoagulants, immunomodulating agents,cytotoxic agents, prophylactic agents, antibiotics, antivirals,antisense, antigens, and antibodies. In some instances, the proteins maybe antibodies or antigens which otherwise would have to be administeredby injection to elicit an appropriate response. Compounds with a widerange of molecular weight can be encapsulated, for example, between 100and 500,000 grams or more per mole.

[0032] Proteins are defined as consisting of 100 amino acid residues ormore; peptides are less than 100 amino acid residues. Unless otherwisestated, the term protein refers to both proteins and peptides. Examplesinclude insulin and other hormones.

[0033] Those therapeutic agents which are charged, such as most of theproteins, including insulin, can be administered as a complex betweenthe charged therapeutic agent and a molecule of opposite charge.Preferably, the molecule of opposite charge is a charged lipid or anoppositely charged protein.

[0034] The particles can include a therapeutic agent for local deliverywithin the lung, such as agents for the treatment of asthma, chronicobstructive pulmonary disease (COPD), emphysema, or cystic fibrosis, orfor systemic treatment. For example, genes for the treatment of diseasessuch as cystic fibrosis can be administered, as can beta agonists,steroids, anticholinergies, and leukotriene modifers for asthma. Otherspecific therapeutic agents include, but are not limited to, humangrowth hormone, insulin, calcitonin, gonadotropin-releasing hormone(“LHRH”), granulocyte colony-stimulating factor (“G-CSF”), parathyroidhormone-related peptide, somatostatin, testosterone, progesterone,estradiol, nicotine, fentanyl, norethisterone, clonidine, scopolamine,salicylate, cromolyn sodium, salmeterol, formeterol, albuterol, andValium.

[0035] The particles can include any of a variety of diagnostic agentsto locally or systemically deliver the agents following administrationto a patient.

[0036] Diagnostic agents also include but are not limited to imagingagents which include commercially available agents used in positronemission tomography (PET), computer assisted tomography (CAT), singlephoton emission computerized tomography, x-ray, fluoroscopy, andmagnetic resonance imaging (MRI).

[0037] Examples of suitable materials for use as contrast agents in MRIinclude but are not limited to the gadolinium chelates currentlyavailable, such as diethylene triamine pentacetic acid (DTPA) andgadopentotate dimeglumine, as well as iron, magnesium, manganese, copperand chromium.

[0038] Examples of materials useful for CAT and x-rays include iodinebased materials for intravenous administration, such as ionic monomerstypified by diatrizoate and iothalamate, non-ionic monomers such asiopamidol, isohexol, and ioversol, non-ionic dimers, such as iotrol andiodixanol, and ionic dimers, for example, ioxagalte.

[0039] Preferably, a therapeutic agent can be present in the spray-driedparticles in an amount ranging from less than about 1% to about 40%.Preferably, a prophylactic agent can be present in the spray-driedparticles in an amount ranging from about less than about 1% to about40%. Preferably, a diagnostic agent can be present in the spray-driedparticles in an amount ranging from about less than about 1% to about40%.

[0040] In one embodiment of the invention, the phospholipid orcombination or phospholipids present in the particles can have atherapeutic, prophylactic or diagnostic role. For example, the particlesof the invention can be used to deliver surfactants to the lung of apatient. This is particularly useful in medical indications whichrequire supplementing or replacing endogenous lung surfactants, forexample in the case of infant respiratory distress syndrome.

[0041] The particles can include other materials. In one embodiment ofthe invention, the particles also include an amino acid. Hydrophobicamino acids are preferred. Suitable amino acids include naturallyoccurring and non-naturally occurring hydrophobic amino acids. Somesuitable naturally occurring hydrophobic amino acids, include but arenot limited to, leucine, isoleucine, alanine, valine, phenylalanine,glycine and tryptophan. Combinations of hydrophobic amino acids can alsobe employed. Non-naturally occurring amino acids include, for example,beta-amino acids. Both D and L configurations and racemic mixtures ofhydrophobic amino acids can be employed. Suitable hydrophobic aminoacids can also include amino acid derivatives or analogs. As usedherein, an amino acid analog includes the D or L configuration of anamino acid having the following formula: —NH—CHR—CO—, wherein R is analiphatic group, a substituted aliphatic group, a benzyl group, asubstituted benzyl group, an aromatic group or a substituted aromaticgroup and wherein R does not correspond to the side chain of anaturally-occurring amino acid. As used herein, aliphatic groups includestraight chained, branched or cyclic C1-C8 hydrocarbons which arecompletely saturated, which contain one or two heteroatoms such asnitrogen, oxygen or sulfur and/or which contain one or more units ofunsaturation. Aromatic groups include carbocyclic aromatic groups suchas phenyl and naphthyl and heterocyclic aromatic groups such asimidazolyl, indolyl, thienyl, furanyl, pyridyl, pyranyl, oxazolyl,benzothienyl, benzofuranyl, quinolinyl, isoquinolinyl and acridintyl.

[0042] Suitable substituents on an aliphatic, aromatic or benzyl groupinclude —OH, halogen (—Br, —Cl, —I and —F) —O(aliphatic, substitutedaliphatic, benzyl, substituted benzyl, aryl or substituted aryl group),—CN, —NO₂, —COOH, —NH₂, —NH(aliphatic group, substituted aliphatic,benzyl, substituted benzyl, aryl or substituted aryl group),—N(aliphatic group, substituted aliphatic, benzyl, substituted benzyl,aryl or substituted aryl group)₂, —COO(aliphatic group, substitutedaliphatic, benzyl, substituted benzyl, aryl or substituted aryl group),—CONH₂, —CONH(aliphatic, substituted aliphatic group, benzyl,substituted benzyl, aryl or substituted aryl group)), —SH, —S(aliphatic,substituted aliphatic, benzyl, substituted benzyl, aromatic orsubstituted aromatic group) and —NH—C(═NH)—NH₂. A substituted benzylicor aromatic group can also have an aliphatic or substituted aliphaticgroup as a substituent. A substituted aliphatic group can also have abenzyl, substituted benzyl, aryl or substituted aryl group as asubstituent. A substituted aliphatic, substituted aromatic orsubstituted benzyl group can have one or more substituents. Modifying anamino acid substituent can increase, for example, the lypophilicity orhydrophobicity of natural amino acids which are hydrophilic.

[0043] A number of the suitable amino acids, amino acids analogs andsalts thereof can be obtained commercially. Others can be synthesized bymethods known in the art. Synthetic techniques are described, forexample, in Green and Wuts, “Protecting Groups in Organic Synthesis”,John Wiley and Sons, Chapters 5 and 7, 1991.

[0044] Hydrophobicity is generally defined with respect to the partitionof an amino acid between a nonpolar solvent and water. Hydrophobic aminoacids are those acids which show a preference for the nonpolar solvent.Relative hydrophobicity of amino acids can be expressed on ahydrophobicity scale on which glycine has the value 0.5. On such ascale, amino acids which have a preference for water have values below0.5 and those that have a preference for nonpolar solvents have a valueabove 0.5. As used herein, the term hydrophobic amino acid refers to anamino acid that,. on the hydrophobicity scale has a value greater orequal to 0.5, in other words, has a tendency to partition in thenonpolar acid which is at least equal to that of glycine.

[0045] Examples of amino acids which can be employed include, but arenot limited to: glycine, proline, alanine, cysteine, methionine, valine,leucine, tyrosine, isoleucine, phenylalanine, tryptophan. Preferredhydrophobic amino acids include leucine, isoleucine, alanine, valine,phenylalanine, glycine and tryptophan. Combinations of hydrophobic aminoacids can also be employed. Furthermore, combinations of hydrophobic andhydrophilic (preferentially partitioning in water) amino acids, wherethe overall combination is hydrophobic, can also be employed.Combinations of one or more amino acids and one or more phospholipids orsurfactants can also be employed. Materials which impart fast releasekinetics to the medicament are preferred.

[0046] The amino acid can be present in the particles of the inventionin an amount of about 60 weight %. Preferably, the amino acid can bepresent in the particles in an amount ranging from about 5 to about 30weight %. The salt of a hydrophobic amino acid can be present in theparticles of the invention in an amount of about 60 weight %.Preferably, the amino acid salt is present in the particles in an amountranging from about 5 to about 30 weight %. Methods of forming anddelivering particles which include an amino acid are described in U.S.patent application Ser. No. 09/382,959, filed on Aug. 25, 1999, entitledUse of Simple Amino Acids to Form Porous Particles During Spray Drying,and U.S. Patent Application filed concurrently herewith under AttorneyDocket No. 2685.1004-001 and entitled Use of Simple Amino Acids to FormPorous Particles; the teachings of both are incorporated herein byreference in their entirety.

[0047] The particles of the invention can have desired drug releaseproperties. In one embodiment, the particles include one or morephospholipids selected according to their transition temperature. Forexample, by administering particles which include a Phospholipid orcombination of phospholipids which have a phase transition temperaturehigher than the patient's body temperature, the release of thetherapeutic, prophylactic or diagnostic agent can be slowed down. On theother hand, rapid release can be obtained by including in the particlesphospholipids having low transition temperatures. Particles havingcontrolled release properties and methods of modulating release of abiologically active agent are described in U.S Provisional ApplicationNo. 60/150,742, entitled Modulation of Release From Dry PowderFormulations by Controlling Matrix Transition, filed on Aug. 25, 1999and U.S. Patent Application filed concurrently herewith under AttorneyDocket No. 2685.1012-001, entitled Modulation of Release From Dry PowderFormulations ; the contents of both are incorporated herein by referencein their entirety.

[0048] Particles, and in particular particles having controlled orsustained release properties, also can include other materials. Forexample, the spray-dried particles can include a biocompatible, andpreferably biodegradable polymer, copolymer, or blend. Such polymers aredescribed, for example, in U.S. Pat. No. 5,874,064, issued on Feb. 23,1999 to Edwards et al., the teachings of which are incorporated hereinby reference in their entirety. Preferred polymers are those which arecapable of forming aerodynamically light particles having a tap densityless than about 0.4 g/cm³, a mean diameter between about 5 μm and about30 μm and an aerodynamic diameter between approximately one and fivemicrons, preferably between one and three microns. The polymers can betailored to optimize different characteristics of the particleincluding: i) interactions between the agent to be delivered and thepolymer to provide stabilization of the agent and retention of activityupon delivery; ii) rate of polymer degradation and, thereby, rate ofdrug release profiles; iii) surface characteristics and targetingcapabilities via chemical modification; and iv) particle porosity.

[0049] Surface eroding polymers such as polyanhydrides can be used toform the particles. For example, polyanhydrides such aspoly[(p-carboxyphenoxy)-hexane anhydride] (PCPH) may be used. Suitablebiodegradable polyanhydrides are described in U.S. Pat. No. 4,857,311.

[0050] In another embodiment, bulk eroding polymers such as those basedon polyesters including poly(hydroxy acids) can be used. For example,polyglycolic acid (PGA), polylactic acid (PLA), or copolymers thereofmay be used to form the particles. The polyester may also have a chargedor functionalizable group, such as an amino acid. In a preferredembodiment, particles with controlled release properties can be formedof poly(D,L-lactic acid) and/or poly(D,L-lactic-co-glycolic acid)(“PLGA”) which incorporate a surfactant such as DPPC.

[0051] Still other polymers include but are not limited to polyamides,polycarbonates, polyalkylenes such as polyethylene, polypropylene,poly(ethylene glycol), poly(ethylene oxide), poly(ethyleneterephthalate), poly vinyl compounds such as polyvinyl alcohols,polyvinyl ethers, and polyvinyl esters, polymers of acrylic andmethacrylic acids, celluloses and other polysaccharides, and peptides.or proteins, or copolymers or blends thereof. Polymers may be selectedwith or modified to have the appropriate stability and degradation ratesin vivo for different controlled drug delivery applications.

[0052] In one embodiment, the particles include functionalized polyestergraft copolymers, as described in Hrkach et al., Macromolecules, 28:4736-4739 (1995); and Hrkach et al., “Poly(L-Lactic acid-co-amino acid)Graft Copolymers: A Class of Functional Biodegradable Biomaterials” inHydrogels and Biodegradable Polymers for Bioapplications, ACS SymposiumSeries No. 627, Raphael M. Ottenbrite et al., Eds., American ChemicalSociety, Chapter 8, pp. 93-101, 1996.

[0053] The particles can also include other materials such as, forexample, buffer salts, dextran, polysaccharides, lactose, trehalose,cyclodextrins, proteins, peptides, polypeptides, fatty acids, inorganiccompounds, phosphates.

[0054] In a preferred embodiment, the particles of the invention have atap density less than about 0.4 g/cm³. Particles which have a tapdensity of less than about 0.4 g/cm³ are referred herein as“aerodynamically light particles”. More preferred are particles having atap density less than about 0.1 g/cm³. Tap density can be measured byusing instruments known to those skilled in the art such as the DualPlatform Microprocessor Controlled Tap Density Tester (Vankel, N.C.) ora GeoPyc™ instrument (Micrometrics Instrument Corp., Norcross, Ga.30093). Tap density is a standard measure of the envelope mass density.Tap density can be determined using the method of USP Bulk Density andTapped Density, United States Pharmacopia convention, Rockville, Md.,10^(th) Supplement, 4950-4951, 1999. Features which can contribute tolow tap density include irregular surface texture and porous structure.

[0055] The envelope mass density of an isotropic particle is defined asthe mass of the particle divided by the minimum sphere envelope volumewithin which it can be enclosed. In one embodiment of the invention, theparticles have an envelope mass density of less than about 0.4 g/cm³.

[0056] Aerodynamically light particles have a preferred size, e.g., avolume median geometric diameter (VMGD) of at least about 5 microns(μm). In one embodiment, the VMGD is from about 5 μm to about 30 μm. Inanother embodiment of the invention, the particles have a VMGD of atleast 9 μm. In other embodiments, the particles have a median diameter,mass median diameter (MMD), a mass median envelope diameter (MMED) or amass median geometric diameter (MMGD) of at least 5 μm, for example fromabout 5 μm and about 30 μm.

[0057] The diameter of the particles, for example, their MMGD or theirVMGD, can be measured using an electrical zone sensing instrument suchas a Multisizer IIe, (Coulter Electronic, Luton, Beds, England), or alaser diffraction instrument (for example Helos, manufactured bySympatec, Princeton, N.J.). Other instruments for measuring particlediameter are well known in the art. The diameter of particles in asample will range depending upon factors such as particle compositionand methods of synthesis. The distribution of size of particles in asample can be selected to permit optimal deposition within targetedsites within the respiratory tract.

[0058] Aerodynamically light particles preferably have “mass medianaerodynamic diameter” (MMAD), also referred to herein as “aerodynamicdiameter”, between about 1 μm and about 5 μm. In one embodiment of theinvention, the MMAD is between about 1 μm and about 3 μm. In anotherembodiment, the MMAD is between about 3 μm and about 5 μm.

[0059] Experimentally, aerodynamic diameter can be determined byemploying a gravitational settling method, whereby the time for anensemble of particles to settle a certain distance is used to inferdirectly the aerodynamic diameter of the particles. An indirect methodfor measuring the mass median aerodynamic diameter (MMAD) is themulti-stage liquid impinger (MSLI).

[0060] The aerodynamic diameter, d_(aer), can be calculated from theequation:

d_(aer)=d_(g){square root}ρ tap

[0061] where d_(g) is the geometric diameter, for example the MMGD and pis the powder density.

[0062] Particles which have a tap density less than about 0.4 g/cm³,median diameters of at least about 5 μm, and an aerodynamic diameter ofbetween about 1 μm and about 5 μm, preferably between about 1 μm andabout 3 μm, are more capable of escaping inertial and gravitationaldeposition in the oropharyngeal region, and are targeted to the airwaysor the deep lung. The use of larger, more porous particles isadvantageous since they are able to aerosolize more efficiently thansmaller, denser aerosol particles such as those currently used forinhalation therapies.

[0063] In comparison to smaller particles the larger aerodynamicallylight particles, preferably having a VMGD of at least about 5 μm, alsocan potentially more successfully avoid phagocytic engulfment byalveolar macrophages and clearance from the lungs, due to size exclusionof the particles from the phagocytes' cytosolic space. Phagocytosis ofparticles by alveolar macrophages diminishes precipitously as particlediameter increases beyond about 3 μm. Kawaguchi, H., et al.,Biomaterials 7: 61-66 (1986); Krenis, L. J. and Strauss, B., Proc. Soc.Exp. Med., 107: 748-750 (1961); and Rudt, S. and Muller, R. H., J.Contr. Rel., 22: 263-272 (1992). For particles of statisticallyisotropic shape, such as spheres with rough surfaces, the particleenvelope volume is approximately equivalent to the volume of cytosolicspace required within a macrophage for complete particle phagocytosis.

[0064] The particles may be fabricated with the appropriate material,surface roughness, diameter and tap density for localized delivery toselected regions of the respiratory tract such as the deep lung or upperor central airways. For example, higher density or larger particles maybe used for upper airway delivery, or a mixture of varying sizedparticles in a sample, provided with the same or different therapeuticagent may be administered to target different regions of the lung in oneadministration. Particles having an aerodynamic diameter ranging fromabout 3 to about 5 μm are preferred for delivery to the central andupper airways. Particles having an aerodynamic diameter ranging fromabout 1 to about 3 μm are preferred for delivery to the deep lung.

[0065] Inertial impaction and gravitational settling of aerosols arepredominant deposition mechanisms in the airways and acini of the lungsduring normal breathing conditions. Edwards, D. A., J. Aerosol Sci., 26:293-317 (1995). The importance of both deposition mechanisms increasesin proportion to the mass of aerosols and not to particle (or envelope)volume. Since the site of aerosol deposition in the lungs is determinedby the mass of the aerosol (at least for particles of mean aerodynamicdiameter greater than approximately 1 μm), diminishing the tap densityby increasing particle surface irregularities and particle porositypermits the delivery of larger particle envelope volumes into the lungs,all other physical parameters being equal.

[0066] The low tap density particles have a small aerodynamic diameterin comparison to the actual envelope sphere diameter. The aerodynamicdiameter, d_(aer), is related to the envelope sphere diameter, d (Gonda,I., “Physico-chemical principles in aerosol delivery,” in Topics inPharmaceutical Sciences 1991 (eds. D. J. A. Crommelin and K. K. Midha),pp. 95-117, Stuttgart: Medpharm Scientific Publishers, 1992)), by theformula:

d_(aer)=d{square root}ρ

[0067] where the envelope mass p is in units of g/cm³. Maximaldeposition of monodispersed aerosol particles in the alveolar region ofthe human lung (˜60%) occurs for an aerodynamic diameter ofapproximately d_(aer)=3 μm. Heyder, J. et al., J. Aerosol Sci., 17:811-825 (1986). Due to their small envelope mass density, the actualdiameter d of aerodynamically light particles comprising a monodisperseinhaled powder that will exhibit maximum deep-lung deposition is:

d=3/{square root}]μm (where ρ<1 g/cm ³);

[0068] where d is always greater than 3 μm. For example, aerodynamicallylight particles that display an envelope mass density, ρ=0.1 g/cm³, willexhibit a maximum deposition for particles having envelope diameters aslarge as 9.5 μm. The increased particle size diminishes interparticleadhesion forces. Visser, J., Powder Technology, 58: 1-10. Thus, largeparticle size increases efficiency of aerosolization to the deep lungfor particles of low envelope mass density, in addition to contributingto lower phagocytic losses.

[0069] The aerodyanamic diameter can be calculated to provide formaximum deposition within the lungs, previously achieved by the use ofvery small particles of less than about five microns in diameter,preferably between about one and about three microns, which are thensubject to phagocytosis. Selection of particles which have a largerdiameter, but which are sufficiently light (hence the characterization“aerodynamically light”), results in an equivalent delivery to thelungs, but the larger size particles are not phagocytosed. Improveddelivery can be obtained by using particles with a rough or unevensurface relative to those with a smooth surface.

[0070] In another embodiment of the invention, the particles have anenvelope mass density, also referred to herein as “mass density” of lessthan about 0.4 g/cm³. Particles also having a mean diameter of betweenabout 5 μm and about 30 μm are preferred. Mass density and therelationship between mass density, mean diameter and aerodynamicdiameter are discussed in U.S. application Ser. No. 08/655,570, filed onMay 24, 1996, which is incorporated herein by reference in its entirety.In a preferred embodiment, the aerodynamic diameter of particles havinga mass density less than about 0.4 g/cm³ and a mean diameter of betweenabout 5 μm and about 30 μm is between about 1 μm and about 5 μm.

[0071] Suitable particles can be fabricated or separated, for example byfiltration or centrifugation, to provide a particle sample with apreselected size distribution. For example, greater than about 30%, 50%,70%, or 80% of the particles in a sample can have a diameter within aselected range of at least about 5 μm. The selected range within which acertain percentage of the particles must fall may be for example,between about 5 and about 30 μm, or optimally between about 5 and about15 μm. In one preferred embodiment, at least a portion of the particleshave a diameter between about 9 and about 11 μm. Optionally, theparticle sample also can be fabricated wherein at least about 90%, oroptionally about 95% or about 99%, have a diameter within the selectedrange. The presence of the higher proportion of the aerodynamicallylight, larger diameter particles in the particle sample enhances thedelivery of therapeutic or diagnostic agents incorporated therein to thedeep lung. Large diameter particles generally mean particles having amedian geometric diameter of at least about 5 μm.

[0072] The invention also relates to methods of preparing particleshaving a tap density less than about 0.4 g/cm³. In one embodiment, themethod includes spray drying a mixture, also referred to herein as a“feed solution”, “feed suspension”, or “feed colloidal suspension” whichincludes a carboxylic acid or salt thereof, a phospholipid orcombination of phospholipids, a multivalent salt and a solvent. In oneembodiment, the mixture also includes a therapeutic, prophylactic ordiagnostic agent.

[0073] Suitable carboxylic acids or salts thereof include, but are notlimited to those described above. The amount of carboxylic acid or saltthereof present in the mixture ranges from about 10 to about 80% weight.The phospholipid or mixture of phospholipids includes, for example, thephospholipids described above. The amount of phospholipid present in themixture ranges from about 20 to about 90% weight. The multivalent saltincludes but is not limited to the multivalent salts described above.The amount of multivalent salt present in the mixture ranges from about5 to about 40% weight. The therapeutic, prophylactic or diagnostic agentincludes but is not limited to the therapeutic, prophylactic ordiagnostic agents described above. The amount of therapeutic,prophylactic or diagnostic agent present in the mixture ranges fromabout less than 1% to about 40% weight.

[0074] Suitable organic solvents that can be employed include but arenot limited to alcohols such as, for example, ethanol, methanol,propanol, isopropanol, butanols, and others. Other organic solventsinclude but are not limited to perfluorocarbons, dichloromethane,chloroform, ether, ethyl acetate, methyl tert-butyl ether and others.Co-solvents that can be employed include an aqueous solvent and anorganic solvent, such as, but not limited to, the organic solvents asdescribed above. Aqueous solvents include, for example, water andbuffered salts. In a preferred embodiment, the co-solvent includes about70/30 ethanol/water by volume. In another preferred embodiment, theco-solvent includes from about 60/40 to about 85/15 ethanol/water.

[0075] In a preferred embodiment the mixture includes a colloidalsolution or colloidal suspension. As used herein, the terms “colloidalsolution” or “colloidal suspension” refer to a system intermediatebetween a true solution and a suspension; the dispersed phase of thecolloidal solution or suspension have a particle size ranging from about1 and 500 nanometers.

[0076] In one embodiment of the invention, the mixture is prepared bysolubilizing a phospholipid in an organic solvent, such as, for exampleethanol, and a carboxylic acid or salt thereof in an aqueous solvent.The two phases are combined and a multivalent salt, such as, forexample, calcium chloride is added thereby forming a fine suspension orcolloidal solution.

[0077] The mixture can have a neutral, acidic or alkaline pH.Optionally, a pH buffer can be added to the solvent or co-solvent or tothe formed mixture. Preferably, the pH can range from about 3 to about10. In one embodiment, the mixture is a miscible mixture of organic andaqueous phases.

[0078] Suitable spray-drying techniques are described, for example, byK. Masters in “Spray Drying Handbook”, John Wiley & Sons, New York,1984. Generally, during spray-drying, heat from a hot gas such as heatedair or nitrogen is used to evaporate the solvent from droplets formed byatomizing a continuous liquid feed. Other spray-drying techniques arewell known to those skilled in the art. In a preferred embodiment, arotary atomizer is employed. An examples of suitable spray driers usingrotary atomization includes the Mobile Minor spray drier, manufacturedby Niro, Denmark. The hot gas can be, for example, air, nitrogen orargon.

[0079] Preferably, the particles of the invention are obtained by spraydrying using an inlet temperature between about 100° C. and about 400°C. and an outlet temperature between about 50° C. and about 130° C.

[0080] Without being held to any mechanistic interpretation of theinvention, it is believed that the formation of a colloidal solutionfacilitates shell formation by (i) providing nucleation sites for theshell to form and (ii) slowing down the diffusion rates of theexcipients in the drying droplet. It is also believed that the presenceof the carboxylate moiety and calcium alters the phase behavior of thephospholipid in solution to create a colloidal aggregate phase thatfacilitates shell formation.

[0081] The spray dried particles can be fabricated with a rough surfacetexture to reduce particle agglomeration and improve flowability of thepowder. The spray-dried particle can be fabricated with features whichenhance aerosolization via dry powder inhaler devices, and lead to lowerdeposition in the mouth, throat and inhaler device.

[0082] Particles including a medicament, for example one or more of thedrugs listed above, are administered to the respiratory tract of apatient in need of treatment, prophylaxis or diagnosis. Administrationof particles to the respiratory system can be by means such as known inthe art. For example, particles are delivered from an inhalation device.In a preferred embodiment, particles are administered via a dry powderinhaler (DPI). Metered-dose-inhalers (MDI), nebulizers or instillationtechniques also can be employed.

[0083] Various suitable devices and methods of inhalation which can beused to administer particles to a patient's respiratory tract are knownin the art. For example, suitable inhalers are described in U.S. Pat.No. 4,069,819, issued Aug. 5, 1976 to Valentini, et al., U.S. Pat. No.4,995,385 issued Feb. 26, 1991 to Valentini, et al., and U.S. Pat. No.5,997,848 issued Dec. 7, 1999 to Patton, et. al. Other examples include,but are not limited to, the Spinhaler® (Fisons, Loughborough, U.K.),Rotahaler® (Glaxo-Wellcome, Research Triangle Technology Park, N.C.),FlowCaps® (Hovione, Loures, Portugal), Inhalator® (Boehringer-Ingelheim,Germany), and the Aerolizer® (Novartis, Switzerland), the diskhaler(Glaxo-Wellcome, RTP, NC) and others, such as known to those skilled inthe art. Preferably, the particles are administered as a dry powder viaa dry powder inhaler.

[0084] The particles of the invention can be employed in compositionssuitable for drug delivery to the pulmonary system. For example, suchcompositions can include the particles and a pharmaceutically acceptablecarrier for administration to a patient, preferably for administrationvia inhalation. The particles can be co-delivered with larger carrierparticles, not including a therapeutic agent, the latter possessing massmedian diameters for example in the range between about 50 μm and about100 μm. The particles can be administered alone or in any appropriatepharmaceutically acceptable carrier, such as a liquid, for examplesaline, or a powder, for administration to the respiratory system.

[0085] The invention is also related to a method for drug delivery tothe pulmonary system. The method comprises administering to therespiratory tract of a patient in need of treatment, prophylaxis ordiagnosis an effective amount of particles, such as described above,comprising a therapeutic, prophylactic or diagnostic agent. As usedherein, the term “effective amount” means an amount required to achievea desired effect, such as, for example, desired therapeutic response, orefficacy. The actual effective amounts of drug can vary according to thespecific drug or combination thereof being utilized, the particularcomposition formulated, the mode of administration, and the age, weight,condition of the patient, and severity of the symptoms or conditionbeing treated. Dosages for a particular patient can be determined by oneof ordinary skill in the art using conventional considerations, (e.g. bymeans of an appropriate, conventional pharmacological protocol).

[0086] Aerosol dosage, formulations and delivery systems also may beselected for a particular therapeutic application, as described, forexample, in Gonda, I. “Aerosols for delivery of therapeutic anddiagnostic agents to the respiratory tract,” in Critical Reviews inTherapeutic Drug Carrier Systems, 6: 273-313, 1990; and in Moren,“Aerosol dosage forms and formulations,” in: Aerosols in Medicine,Principles, Diagnosis and Therapy, Moren, et al., Eds, Esevier,Amsterdam, 1985.

[0087] Preferably, particles administered to the respiratory tracttravel through the upper airways (oropharynx and larynx), the lowerairways which include the trachea followed by bifurcations into thebronchi and bronchioli and through the terminal bronchioli which in turndivide into respiratory bronchioli leading then to the ultimaterespiratory zone, the alveoli or the deep lung. In a preferredembodiment of the invention, most of the mass of particles deposits inthe deep lung. In another embodiments of the invention, delivery isprimarily to the central airways. Delivery to the upper airways can alsobe obtained.

[0088] In one embodiment of the invention, delivery to the pulmonarysystem of particles is in a single, breath-actuated step, as describedin U.S. Patent Application, High Efficient Delivery of a LargeTherapeutic Mass Aerosol, application Ser. No. 09/591,307, filed Jun. 9,2000, Attorney Docket No. 2685.2001-000, which is incorporated herein byreference in its entirety. In another embodiment of the invention, atleast 50% of the mass of the particles stored in the inhaler receptacleis delivered to a subject's respiratory system in a single,breath-activated step. In a further embodiment, at least 5 milligramsand preferably at least 10 milligrams of a medicament is delivered byadministering, in a single breath, to a subject's respiratory tractparticles enclosed in the receptacle. Amounts as high as 15, 20, 25, 30,35, 40 and 50 milligrams can be delivered.

[0089] Porous or aerodynamically light particles, having a geometricsize (or mean diameter) in the range of about 5 to about 30 μm, and tapdensity less than about 0.4 g/cm³, such that they possess an aerodynamicdiameter of about 1 and about 3 μm, have been shown to display idealproperties for delivery to the deep lung. Larger aerodynamic diameters,ranging, for example, from about 3 to about 5 μm are preferred, however,for delivery to the central and upper airways. According to oneembodiment of the invention the particles have a tap density of lessthan about 0.4 g/cm³ and a mean diameter of between about 5 μm and about30 ∞m. According to another embodiment of the invention, the particleshave a mass density of less than about 0.4 g/cm³ and a mean diameter ofbetween about 5 μm and about 30 μm. In one embodiment of the invention,the particles have an aerodynamic diameter between about 1 μm and about5 μm. In another embodiment of the invention, the particles have anaerodynamic diameter between about 1 μm and about 3 μm microns. In stillanother embodiment of the invention, the particles have an aerodynamicdiameter between about 3 μm and about 5 μm.

[0090] In one embodiment of the invention, the particles areadministered to the respiratory system of a comatose, unconscious oranesthetized patient. In another embodiment, the particles areadministered to the respiratory system of a nonhuman mammal, for examplein veterinary medicine or animal model experimental work. In a furtherembodiment of the invention, the particles are administered to sitesother than the pulmonary system.

[0091] The present invention will be further understood by reference tothe following non-limiting examples.

[0092] Exemplifications

[0093] Some of the methods and materials employed in the followingexamples are described in U.S. application Ser. No. 09/211,940, filedDec. 15, 1998, in U.S. application Ser. No. 08/739,308, filed Oct. 29,1996, now U.S. Pat. No. 5,874,064, in U.S. application Ser. No.08/655,570, filed May 24, 1996, in U.S. application Ser. No. 09/194,068,filed May 23, 1997, in PCT/US97/08895 application filed May 23, 1997, inU.S. application Ser. No. 08/971,791, filed Nov. 17, 1997, in U.S.application Ser. No. 08/784,421, filed Jan. 16, 1997, now U.S. Pat. No.5,855,913 and in U.S. application Ser. No. 09/337,245, filed on Jun. 22,1999, all of which are incorporated herein by reference in theirentirety.

[0094] Materials

[0095] Citric acid and calcium chloride were obtained from SpectrumLabs, Laguna Hills, Calif. DPPC was obtained from Avanti (Alabaster,Ala.).

[0096] Spray Drying

[0097] A Mobile Minor spray-drier from Niro (Denmark) was used. The gasemployed was dehumidified air. The gas temperature ranged from about 80to about 150° C. The atomizer speed ranged from about 15,000 to about50,000 RPM. The gas rate was 70 to 92 kg/hour and the liquid feed rateranged from about 50 to about 100 ml/minute.

[0098] Geometric Size Distribution Analysis

[0099] Size distributions were determined using a Coulter Multisizer II.Approximately 5-10 mg of powder was added to 50 mL isoton II solutionuntil the coincidence of particles was between 5 and 8%. Greater than500,000 particles were counted for each batch of spheres.

[0100] Aerodynamic Size Distribution Analysis

[0101] Aerodynamic size distribution was determined using anAerosizer/Aerodispenser (Amherst Process Instruments, Amherst, Mass.).Approximately 2 mg powder was introduced into the Aerodisperser and theAerodynamic size was determined by time of flight measurements.

[0102] Particle Morphology by Scanning Electron Microscopy (SEM)

[0103] Microsphere morphology was observed by scanning electronmicroscopy (SEM) using a Stereoscan 250 MK3 microscope from CambridgeInstruments (Cambridge, Mass.) at 15 kV. Microspheres were freeze-dried,mounted on metal stubs with double-sided tape, and coated with goldprior to observation.

[0104] Particle Density Analysis

[0105] Bulk density was estimated by tap density measurements, such asobtained using a Dual Platform Microprocessor Controlled Tap DensityTester (Vankel, N.C.) and confirmed by mercury intrusion analysis atPorous Materials, Inc. (Ithaca, N.Y.).

EXAMPLE 1

[0106] 300 milliliters of an aqueous solution containing 0.07% sodiumcitrate buffered to PH: 7.0 via addition of HCl was combined with 700milliliters of ethanol solution containing 0.1% DPPC. Four millilitersof a 2.5% aqueous CaCl₂ solution was added to the stirred mixture, atwhich point the colloidal solution was formed.

[0107] The mixture was spray dried. Inlet temperature was about 110 C.,Feed rate about 60-70 m/min and atomizer spin rate 15000-20000 RPM. Thetap density of the particles obtained ranged from 0.05 to 0.1 g/cm³.Yield was about 35-50%. The median geometric diameter of the resultingparticles was 10.7 microns and the median aerodynamic diameter was 2.2microns. SEM data of these particles indicated that they have a crumpledpaper like morphology.

EXAMPLE 2

[0108] The mixture was prepared and spray dried as described above. Theaqueous phase (300 ml, 200 mg Na-Citrate, pH=7.0) and the ethanol phase(700 ml, 700 mg DPPC) were mixed and stirred. CaCl₂ (25 mg/mg aqueoussolution) was added dropwise. Amounts of calcium chloride used are shownand the properties of the particles obtained are shown in Table 1. TABLE1 Amount of VMGD MMAD Est. Tap CaCl2 added Yield (%) (microns) (microns)Density  0 mg ˜0 — — —  50 mg 15 6.62 3.35 0.26  75 mg 41 9.62 2.66 0.08100 mg 36 9.72 2.39 0.06 125 mg 36 9.06 2.66 0.09

EXAMPLE 3

[0109] Particles containing albuterol sulfate were prepared in thefollowing manner. A mixture including 66% DPPC, 20% sodium citrate, 10%calcium chloride and 4% albuterol sulfate was formed in a 70/30 (v/v)ethanol/water cosolvent system as described above and spray-dried. Themedian geometric diameter of the resulting particles was 9.2 microns andthe mass mean aerodynamic diameter was 2.5 microns.

[0110] While this invention has been particularly shown and describedwith references to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the scope of the inventionencompassed by the appended claims.

What is claimed is:
 1. A method of preparing particles having a tapdensity less than about 0.4 g/cm³ comprising: (a) forming a mixtureincluding: a therapeutic, prophylactic or diagnostic agent, or anycombination thereof, a carboxylic acid or a salt thereof, aphospholipid, a multivalent salt and a solvent; and (b) spray-dryingsaid mixture to produce particles having a tap density less than about0.4 g/cm³.
 2. The method of claim 1 wherein the particles have a mediangeometric diameter of between about 5 microns and about 30 microns. 3.The method of claim 1 wherein the particles have an aerodynamic diameterof between about 1 and about 5 microns.
 4. The method of claim 3 whereinthe particles have an aerodynamic diameter of between about 1 and about3 microns.
 5. The method of claim 3 wherein the particles have anaerodynamic diameter of between about 3 and about 5 microns.
 6. Themethod of claim 1 wherein the carboxylic acid includes at least twocarboxyl groups.
 7. The method of claim 1 wherein the carboxylic acid isa hydroxydicarboxylic acid or a hydroxytricarboxylic acid.
 8. The methodof claim 1 wherein the carboxylic acid is citric acid.
 9. The method ofclaim 1 wherein the carboxylic acid is present in the mixture in anamount of at least about 10% weight.
 10. The method of claim 1 whereinthe phospholipid is endogenous to the lung.
 11. The method of claim 1wherein the phospholipid is selected from the group consisting ofphosphatidylcholines, phosphatidylethanolamines, phosphatidylglycerols,phophstidylserines, phosphatidylinositols and combinations thereof. 12.The method of claim 1 wherein the phospholipid is present in the mixturein an amount of at least about 20% weight.
 13. The method of claim 1wherein the multivalent salt is a salt of an alkaline earth metal. 14.The method of claim 1 wherein the multivalent salt is a chloride. 15.The method of claim 1 wherein the multivalent salt is calcium chloride.16. The method of claim 1 wherein the multivalent salt is present in themixture in an amount of at least about 5% weight.
 17. The method ofclaim 1 wherein the agent is albuterol.
 18. The method of claim 1wherein the therapeutic, prophylactic or diagnostic agent is present inthe mixture in an amount between about less than 1% and about 40%weight.
 19. The method of claim 1 wherein solvent includes an organicsolvent.
 20. The method of claim 1 wherein the solvent includes anaqueous organic co-solvent.
 21. The method of claim 1 wherein themixture is a colloidal solution.